The invention relates generally to striking elements for producing mechanical shocks transmitted to a tool.
Striking elements are well known as parts of an impact tool. They produce shocks and transmit them to the tool belonging to the impact tool. Mention may be made here, for example, of percussion drills, wherein an unbalanced mass connected to the drill drive acts as the striking element which, when the drill is operated as a tool, additionally allows it to execute axial shocks.
A striking element used chiefly in surgery is described in EP 0,452,543 A1. There a single piston, displaceable in a cylinder by compressed air, does the work. On a forward stroke--directed against a tool connected to the striking element--this piston acts on a first impact surface, and this shock is transmitted to the tool. On its subsequent return stroke the piston acts on a second impact surface. The tool--a rasp, for example, is mentioned there --is successively exposed to a forward-thrust working shock and an opposing loosening shock. At least one high-pressure channel between the first and the second impact surfaces is present in the striking element, by which the pressure necessary for motion of the piston is built up during the motion cycle. In addition, at least one inlet and one outlet are provided for compressed air.
For the construction of this striking element, a total volume consisting of a first partial volume, which lies between the first impact surface and the piston area belonging to it, and the volume of the high-pressure channel is determined at particular positions of the piston. The necessary pressure may be built up and the striking element functions only when the ratio of the value of this total volume to the area of the active first impact surface and of the second impact surface exceeds predetermined values. Embodiments are indicated by which the loosening shock may in each instance be suppressed either permanently or at times.
The striking element according to EP 0,452,543 has a relatively complicated mechanical structure. For example, it has two different diameters for the cylindrical bore and the piston diameter, a column running within the piston and a total of six impact surfaces requiring machining. Compared to the overall arrangement of the striking element, the piston itself has only a small mass. Since the pressure in the volume between the respective impact plate and the associated piston area is built up or let down only during its motion, the piston motions proceed relatively slowly, so that the energy transmitted to the tool by the piston motions per unit of time is relatively small.
Therefore an object of the invention is to procure a striking element which, with external dimensions comparable to those of the striking element described above, achieves a higher striking rate and transmits a greater amount of energy to the tool per shock.